1. Field of the Invention
The present invention relates to a process for producing neopentyl glycol. More particularly, it is concerned with a process for producing neopentyl glycol (2,2-dimethyl-1,3-propanediol) by hydrogenating hydroxypivaldehyde (2,2-dimethyl-3-hydroxy propanal) as obtained by the condensation of isobutyraldehyde and formaldehyde, in the presence of a three-component catalyst of platinum-ruthenium-tungsten (hereinafter abbreviated to "Pt-Ru-W"). 2. Description of Related Arts
Neopentyl glycol is a very important intermediate for industrial use and has a wide variety of applications; for example, it is used in production of various synthetic resins such as acrylic resins, polyester resins, polyurethane resins, alkyd resins and polycarbonate resins, a plasticizer, a synthetic lubricating oil, a synthetic drying oil, a fiber processing agent, or a surfactant.
Neopentyl glycol has been usually produced by the following two methods.
In accordance with one of the methods, isobutyraldehyde and formaldehyde are subjected to an aldol condensation reaction and then to a crossed Cannizzaro reaction in the presence of a strongly alkaline catalyst, e.g. caustic soda, caustic potash or calcium hydroxide to thereby obtain the desired neopentyl glycol. This method, however, has a disadvantage in that sodium formate is also produced in an equimolar amount to the desired product. Therefore, unless sodium formate is effectively utilized, the method is unsuitable for use in production of neopentyl glycol on a commercial scale.
In accordance with another method, hydroxypivaldehyde, as obtained by the reaction of isobutyraldehyde and formaldehyde, is hydrogenated in the presence of a catalyst to thereby produce the desired neopentyl glycol, which is not accompanied by the production of sodium formate. This method is disclosed in Japanese Patent Publication Nos. 33169/1974, 17568/1678, U.S. Pat. Nos. 1,048,530, 1,219,162, 3,920,760, 4,021,496, West German Patent No. 1,014,089, European Patent Nos. 44,421, 44,444. In these patents, Raney nickel, Ni-Cr, Cu-Zn, Cu-Al, Cu-Cr and Cr-Ba catalysts are disclosed as catalysts for use in the hydrogenation reaction.
These conventional catalysts suffer from problems in that catalytic activity is insufficient and thus the reaction must be carried out under high pressure conditions, and that catalytic activity cannot be maintained at a high level for a long period of time since it is decreased under the influences of small amounts of impurities contained in hydroxypivaldehyde as the starting material. In the case of the Raney nickel catalyst, various problems arise; for example, preparation and handling of the catalyst are not easy, catalytic activity is insufficient and furthermore it cannot be maintained for a long time, and since the catalyst is used in a slurry form, the process inevitably becomes complicated.